Thermal control for formation and processing of aluminum nitride

Abstract

In various embodiments, controlled heating and/or cooling conditions are utilized during the fabrication of aluminum nitride single crystals and aluminum nitride bulk polycrystalline ceramics. Thermal treatments may also be utilized to control properties of aluminum nitride crystals after fabrication.

What is claimed is: 
     
       1. A single-crystal AlN substrate having (i) a diameter of at least approximately 30 mm and (ii) an ultraviolet (UV) transparency metric ranging from approximately 5 cm 3  to approximately 5000 cm 3  at a wavelength of interest of 265 nm, the UV transparency metric being defined in cm 3  as: 
       
         
           
             
               d 
               
                 10 
                 × 
                 FWHM 
                 × 
                 
                   α 
                   2 
                 
               
             
           
         
         wherein d is a diameter of the AlN substrate in mm, FWHM is a full-width at half-maximum of an x-ray diffraction curve of the AlN substrate in radians, and a is an absorption coefficient of the AlN substrate at the wavelength of interest. 
       
     
     
       2. The AlN substrate of  claim 1 , wherein the diameter of the AlN substrate is at least approximately 50 mm. 
     
     
       3. The AlN substrate of  claim 1 , wherein a diameter of the AlN substrate is no greater than approximately 150 mm. 
     
     
       4. The AlN substrate of  claim 1 , wherein a thermal conductivity of the AlN substrate is approximately 290 W/mK or greater at room temperature. 
     
     
       5. The AlN substrate of  claim 1 , wherein a crystalline orientation of the AlN substrate is substantially parallel to a c-axis. 
     
     
       6. The AlN substrate of  claim 1 , wherein a crystalline orientation of the AlN substrate is angled at least approximately 10° relative to a c-axis. 
     
     
       7. The AlN substrate of  claim 1 , further comprising a light-emitting device disposed thereover. 
     
     
       8. The AlN substrate of  claim 7 , wherein the light-emitting device is configured to emit ultraviolet light. 
     
     
       9. The AlN substrate of  claim 7 , wherein the light-emitting device comprises a light-emitting diode or a laser. 
     
     
       10. The AlN substrate of  claim 1 , wherein a density of threading edge dislocations in the AlN substrate is less than 5×10 3  cm −2 . 
     
     
       11. The AlN substrate of  claim 1 , wherein a density of threading screw dislocations in the AlN substrate is less than 10 cm −2 . 
     
     
       12. The AlN substrate of  claim 1 , wherein a silicon concentration of the AlN substrate is less than 1×10 17  cm −3 . 
     
     
       13. The AlN substrate of  claim 1 , wherein an oxygen concentration of the AlN substrate is less than 1×10 17  cm −3 . 
     
     
       14. The AlN substrate of  claim 1 , wherein a carbon concentration of the AlN substrate is less than 3×10 17  cm −3 . 
     
     
       15. The AlN substrate of  claim 1 , wherein a ratio of the carbon concentration of the AlN substrate to the oxygen concentration of the AlN substrate is less than 0.5. 
     
     
       16. The AlN substrate of  claim 1 , wherein a thickness of the substrate is 100 μm or greater. 
     
     
       17. The AlN substrate of  claim 1 , wherein a thickness of the substrate is 200 μm or greater. 
     
     
       18. The AlN substrate of  claim 1 , wherein a thickness of the substrate is 2 mm or greater. 
     
     
       19. The AlN substrate of  claim 1 , further comprising an epitaxial semiconductor layer disposed thereover.